598 research outputs found
Spatial Distribution of Nucleosynthesis Products in Cassiopeia A: Comparison Between Observations and 3D Explosion Models
We examine observed heavy element abundances in the Cassiopeia A supernova
remnant as a constraint on the nature of the Cas A supernova. We compare bulk
abundances from 1D and 3D explosion models and spatial distribution of elements
in 3D models with those derived from X-ray observations. We also examine the
cospatial production of 26Al with other species. We find that the most reliable
indicator of the presence of 26Al in unmixed ejecta is a very low S/Si ratio
(~0.05). Production of N in O/S/Si-rich regions is also indicative. The
biologically important element P is produced at its highest abundance in the
same regions. Proxies should be detectable in supernova ejecta with high
spatial resolution multiwavelength observations.Comment: To appear in the Conference Proceedings for the "10th Symposium on
Nuclei in the Cosmos (NIC X)", July 27 - August 1 2008, Mackinack Island,
Michigan, US
Preventing Response Elimination Strategies Improves the Convergent Validity of Figural Matrices
Several studies have shown that figural matrices can be solved with one of two strategies: (1) Constructive matching consisting of cognitively generating an idealized response, which is then compared with the options provided by the response format; or (2) Response elimination consisting of comparing the response format with the item stem in order to eliminate incorrect responses. A recent study demonstrated that employing a response format that reduces response elimination strategies results in higher convergent validity concerning general intelligence. In this study, we used the construction task, which works entirely without distractors because the solution has to be generated in a computerized testing environment. Therefore, response elimination is completely prevented. Our results show that the convergent validity of general intelligence and working memory capacity when using a test employing the construction task is substantially higher than when using tests employing distractors that followed construction strategies used in other studies. Theoretical as well as practical implications of this finding are discussed
ESTRO IORT Task Force/ACROP recommendations for intraoperative radiation therapy in borderline-resected pancreatic cancer
Radiation therapy (RT) is a valuable component of multimodal treatment for localized pancreatic cancer.
Intraoperative radiation therapy (IORT) is a very precise RT modality to intensify the irradiation effect for
cancer involving upper abdominal structures and organs, generally delivered with electrons (IOERT).
Unresectable, borderline and resectable disease categories benefit from dose-escalated chemoradiation
strategies in the context of active systemic therapy and potential radical surgery. Prolonged preoperative
treatment may act as a filter for selecting patients with occult resistant metastatic disease. Encouraging
survival rates have been documented in patients treated with preoperative chemoradiation followed by
radical surgery and IOERT (>20 months median survival, >35% survival at 3 years). Intensive preoperative
treatment, including induction chemotherapy followed by chemoradiation and an IOERT boost, appears
to prolong long-term survival within the subset of patients who remain relapse-free for>2 years
(>30 months median survival; >40% survival at 3 years). Improvement of local control through higher
RT doses has an impact on the survival of patients with a lower tendency towards disease spread.
IOERT is a well-accepted approach in the clinical scenario (maturity and reproducibility of results), and
extremely accurate in terms of dose-deposition characteristics and normal tissue sparing. The technique
can be adapted to systemic therapy and surgical progress. International guidelines (National
Comprehensive Cancer Network or NCCN guidelines) currently recommend use of IOERT in cases of close
surgical margins and residual disease. We hereby report the ESTRO/ACROP recommendations for performing IOERT in borderline-resectable pancreatic cancer
Intensity modulated proton arc therapy via geometry-based energy selection for ependymoma
We developed a novel method of creating intensity modulated proton arc
therapy (IMPAT) plans that uses computing resources efficiently and may offer a
dosimetric benefit for patients with ependymoma or similar tumor geometries.
Our IMPAT planning method consists of a geometry-based energy selection step
with major scanning spot contributions as inputs computed using ray-tracing and
single-Gaussian approximation of lateral spot profiles. Based on the geometric
relation of scanning spots and dose voxels, our energy selection module selects
a minimum set of energy layers at each gantry angle such that each target voxel
is covered by sufficient scanning spots as specified by the planner, with dose
contributions above the specified threshold. Finally, IMPAT plans are generated
by robustly optimizing scanning spots of the selected energy layers using a
commercial proton treatment planning system. The IMPAT plan quality was
assessed for four ependymoma patients. Reference three-field IMPT plans were
created with similar planning objective functions and compared with the IMPAT
plans. In all plans, the prescribed dose covered 95% of the clinical target
volume (CTV) while maintaining similar maximum doses for the brainstem. While
IMPAT and IMPT achieved comparable plan robustness, the IMPAT plans achieved
better homogeneity and conformity than the IMPT plans. The IMPAT plans also
exhibited higher relative biological effectiveness (RBE) enhancement than did
the corresponding reference IMPT plans for the CTV in all four patients and
brainstem in three of them. The proposed method demonstrated potential as an
efficient technique for IMPAT planning and may offer a dosimetric benefit for
patients with ependymoma or tumors in close proximity to critical organs. IMPAT
plans created using this method had elevated RBE enhancement associated with
increased linear energy transfer.Comment: 24 pages with 8 figures and 2 table
The analytic structure of heavy quark propagators
The renormalised quark Dyson-Schwinger equation is studied in the limit of
the renormalised current heavy quark mass m_R --> infinity. We are particularly
interested in the analytic pole structure of the heavy quark propagator in the
complex momentum plane. Approximations in which the quark-gluon vertex is
modelled by either the bare vertex or the Ball-Chiu Ansatz, and the Landau
gauge gluon propagator takes either a gaussian form or a gaussian form with an
ultraviolet asymptotic tail are used.Comment: 21 pages Latex and 5 postscript figures. The original version of this
paper has been considerably extended to include a formalism dealing with the
renormalised heavy quark Dyson-Schwinger equation and uses a more realistic
Ansatz for the gluon propagator
Impaired Relaxation and Reduced Lusitropic Reserve in Atrial Myocardium in the Obese Patients
Background: Obesity can influence the structure and function of the atrium, but most studies focused on the relationship of body mass index (BMI) and overt left atrium (LA) dysfunction as assessed by clinical imaging. We combined the assessment of right atrium (RA) function in vivo and in vitro in obese and non-obese patients scheduled for elective cardiac surgery.
Methods: Atrial structure and function were quantified pre-operatively by echocardiography. RA tissue removed for the establishment of extracorporeal support was collected and RA trabeculae function was quantified in vitro at baseline and with adrenergic stimulation (isoproterenol). Fatty acid-binding protein 3 (FABP3) was quantified in RA tissue. Results were stratified according to the BMI of the patients.
Results: About 76 patients were included pre-operatively for the echocardiographic analysis. RA trabeculae function at baseline was finally quantified from 46 patients and RA function in 28 patients was also assessed with isoproterenol. There was no significant correlation between BMI and the parameters of atrial function measured by the clinical echocardiography. However, in vitro measurements revealed a significant correlation between BMI and a prolonged relaxation of the atrial myocardium at baseline, which persisted after controlling for the atrial fibrillation and diabetes by the partial correlation analysis. Acceleration of relaxation with isoproterenol was significantly lower in the obese group (BMI ≥ 30 kg/m(2)). As a result, relaxation with adrenergic stimulation in the obese group remained significantly higher compared to the overweight group (25 kg/m(2) ≤ BMI < 30 kg/m(2), p = 0.027) and normal group (18.5 kg/m(2) ≤ BMI < 25 kg/m(2), p = 0.036). There were no differences on impacts of the isoproterenol on (systolic) developed force between groups. The expression of FABP3 in the obese group was significantly higher compared to the normal group (p = 0.049) and the correlation analysis showed the significant correlations between the level of FABP3 in the RA trabeculae function.
Conclusion: A higher BMI is associated with the early subclinical changes of RA myocardial function with the slowed relaxation and reduced adrenergic lusitropy
What happens if you single out? An experiment
We present an experiment investigating the effects of singling out an individual on trust and trustworthiness. We find that (a) trustworthiness falls if there is a singled out subject; (b) non-singled out subjects discriminate against the singled out subject when they are not responsible of the distinct status of this person; (c) under a negative frame, the singled out subject returns significantly less; (d) under a positive frame, the singled out subject behaves bimodally, either selecting very low or very high return rates. Overall, singling out induces a negligible effect on trust but is potentially disruptive for trustworthiness
The impact of XENON100 and the LHC on Supersymmetric Dark Matter
The effect of 2010 and 2011 LHC data are discussed in connection to the
potential for the direct detection of supersymmetric dark matter. The impact of
the recent XENON100 results are contrasted to these predictions.Comment: 14 pages, 23 figures, To be published in the Proceedings of the 7th
DSU Conference, Beijing Chin
Signaling in Secret: Pay-for-Performance and the Incentive and Sorting Effects of Pay Secrecy
Key Findings: Pay secrecy adversely impacts individual task performance because it weakens the perception that an increase in performance will be accompanied by increase in pay; Pay secrecy is associated with a decrease in employee performance and retention in pay-for-performance systems, which measure performance using relative (i.e., peer-ranked) criteria rather than an absolute scale (see Figure 2 on page 5); High performing employees tend to be most sensitive to negative pay-for- performance perceptions; There are many signals embedded within HR policies and practices, which can influence employees’ perception of workplace uncertainty/inequity and impact their performance and turnover intentions; and When pay transparency is impractical, organizations may benefit from introducing partial pay openness to mitigate these effects on employee performance and retention
The temporal reliability of serum estrogens, progesterone, gonadotropins, SHBG and urinary estrogen and progesterone metabolites in premenopausal women
BACKGROUND: There is little existing research to guide researchers in estimating the minimum number of measurement occasions required to obtain reliable estimates of serum estrogens, progesterone, gonadotropins, sex hormone-binding globulin (SHBG), and urinary estrogen and progesterone metabolites in premenopausal women. METHODS: Using data from a longitudinal study of 34 women with a mean age of 42.3 years (SD = 2.6), we calculated the minimum number of measurement occasions required to obtain reliable estimates of 12 analytes (8 in blood, 4 in urine). Five samples were obtained over 1 year: at baseline, and after 1, 3, 6, and 12 months. We also calculated the percent of true variance accounted for by a single measurement and intraclass correlation coefficients (ICC) between measurement occasions. RESULTS: Only 2 of the 12 analytes we examined, SHBG and estrone sulfate (E(1)S), could be adequately estimated by a single measurement using a minimum reliability standard of having the potential to account for 64% of true variance. Other analytes required from 2 to 12 occasions to account for 81% of the true variance, and 2 to 5 occasions to account for 64% of true variance. ICCs ranged from 0.33 for estradiol (E(2)) to 0.88 for SHBG. Percent of true variance accounted for by single measurements ranged from 29% for luteinizing hormone (LH) to 92% for SHBG. CONCLUSIONS: Experimental designs that take the natural variability of these analytes into account by obtaining measurements on a sufficient number of occasions will be rewarded with increased power and accuracy
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